The present invention relates to a fuel injector.
U.S. Pat. No. 4,946,107 describes an electromagnetically operable fuel injection valve, which has a non-magnetic sleeve as a connecting part between a core and a valve-seat body. The sleeve is securely fixed with its two axial ends to the core and to the valve-seat body. The sleeve has a constant external diameter and a constant internal diameter over its entire axial length and, accordingly, has same-size inlet orifices at both of its ends. The core and the valve-seat body are so formed with respect to their outer diameter that they extend into the sleeve at both ends, so that the sleeve fully surrounds the two component parts, core and valve-seat body, in these inwardly projecting areas. A valve needle moves axially within the sleeve and has an armature which is guided through the sleeve. The sleeve is permanently joined to the core and to the valve-seat body by welding, for example, as described in German Patent Application No. 43 10 819, which also describes using a thin-walled, non-magnetic sleeve as a connecting part between the core and valve-seat body of a fuel injector. In terms of its structural design, this sleeve corresponds substantially to the sleeve described in U.S. Pat. No. 4,946,107. The tubular sleeves make it possible to reduce the volume and the weight of the fuel injectors.
One of the advantages of the fuel injector of the present invention is that it makes it possible, in a simple and cost-effective manner, to further diminish the volume and weight of the fuel injector and to fulfill a greater number of functions using only one sleeve-shaped component part. In addition to the benefit of lower manufacturing costs, it is also simpler to assemble the fuel injector because it entails comparatively few production steps. The present invention achieves these advantages by employing a thin-walled, non-magnetic sleeve as a connecting part between a core and a valve-seat body in the fuel injector, said non-magnetic sleeve also fulfilling the retaining, supporting or holding (seating) functions. Thus at its one axial end, the sleeve has a bottom section which runs normal to the axial extent of the sleeve and which assures an optimal and secure attachment of the valve-seat body and increases sleeve stability. A major factor in reducing the volume and weight is that the sleeve extends over more than half of the axial length of the fuel injector and can, therefore, even assume the function of a fuel intake fitting.
It is also advantageous to press a valve-seat body having a valve-seat surface into the sleeve, the bottom section of the sleeve providing a contact surface to prevent the valve-seat body from slipping.
It is further advantageous to produce the sleeve by deep drawing the sheet metal, as this method is simple and economical and, nevertheless, meets the required precision.
For xe2x80x9cside-feedxe2x80x9d injectors, which are partially traversed by a transverse flow, it is advantageous to provide bores or orifices in the inner sleeve wall to assure a direct fuel supply to the spray orifices of the fuel injector.
One particular benefit is attained by providing the bottom section of the sleeve with the spray orifices for metering fuel arranged therein. This is especially cost-effective, since one can then eliminate one component part (spray-orifice plate) and its associated joint.
It is also advantageous to design the sleeve to be long enough to extend over the entire axial extension length of the fuel injector. This enables the sleeve to assume the function of a fuel intake fitting as well. Furthermore, the core can be easily pressed into the sleeve, making it simple to adjust the valve needle lift Moreover, the problem of seal tightness toward the interior valve space is eliminated in this long sleeve arrangement. A top sealing ring provides a direct sealing action on the sleeve.
Another advantage achieved by the sleeve configuration is that valve needles or armatures of the same design can be installed for completely different types of valves.